1. Field of the Invention
This invention relates to a developer unit with a toner supply and a toner application device, wherein toner is applied to a developer device, and the toner can be brought into planar contact with an OPC.
2. Discussion of Related Art
Such a developer unit is known from European Patent Reference EP 1 213 621 A. In this case the developer unit has an exchangeable toner supply reservoir, from which toner is metered into a developer housing. The toner is applied by an application roller to the surface of the developer roller. The developer roller rolls off on an OPC, namely a photo-conductor drum, and in the process transfers the toner material. The OPC is known and has a latent charge image. The contact area between the developer roller and the OPC is embodied in the shape of a so-called “nip”. Here, the rigid OPC surface penetrates into the elastically yielding surface of the developer roller. A planar contact area results accordingly, which has an extension in the circumferential surface of the OPC in a range of approximately 4 to 10 mm. The squeezed area between the OPC and the developer roller formed by this arrangement forms a non-defined deformation within which the circumferential velocity of the surface of the developer roller varies. In contrast, the surface velocity of the OPC is constant. Because of speed differences, this can lead to smearing of the toner in the contact area. Also, because of the centrifugal force prevailing in the squeezed area, toner particles with a large inherent weight, in particular, can be prematurely released from the developer roller prior to the actual contact area. This leads to scattering effects, which impair the sharpness of the printed image.